In June 2013 I wrote a review of the Berghaus Freeflow 25 + 5 rucksack. My review was generally positive and I stated it was the best rucksack I'd ever used. However, I haven't used it for several months now because although it was excellent when on my back it was a bit of a nuisance when travelling on public transport. It wouldn't stand upright on the floor or on a seat, and was too large to go in the luggage rack on the train, and it was very difficult to take off in a confined space.
I would still recommend the 25 + 5 if you're travelling by car, but not for using on public transport. The 'Freeflow' system is excellent at keeping your back from being rubbed and from sweating, and there are plenty of useful pockets, pouches, straps and hooks to keep everything secure and accessible...but I think that when it was designed they didn't take into account a large man like myself (6ft 4ins and 20st) taking it on a bus or a train.